static class MyServerExampleWithFrq implements Closeable {
    private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();

    private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();

    private final ServerSocket serverSocket;

    private MyServerExampleWithFrq() throws IOException {
      this.serverSocket = new ServerSocket(0);
    }